Technical Field
The present invention relates to operating instruments and spinal implants adapted thereto which can be inserted into the intervertebral space from all usual, conventional, and less or minimally invasive access variants and, for example in the case of TLIF or PLIF, can be brought into the optimal permanent position locally in a mechanically safe manner.
Related Background Art
In the event of advanced degeneration of intervertebral discs in the lumbar spine region, stiffening surgery is often the best option for treatment. For this, the remains of the worn intervertebral discs are removed, and bone or bone replacement material is inserted into the defect with the aim of a fusion, i.e. the adjacent vertebrae joining to form a block. First of all, it is important to ensure the mechanical stability required for bone healing, and secondly, to restore the geometrical (=anatomical) conditions which are necessary for undisturbed nerve function. In order to ensure this, placeholder implants, so-called “cages”, have been used all over the world for the reconstruction of the vertebral body column which is located in front of the thecal sac. The direct implantation path to this leads accordingly through the abdomen and is used when conventionally open (anterior lumbar interbody fusion, ALIF) or even minimally invasive (e.g. XLIF, OLIF) surgical access techniques are used. However, because most of these pathologies also require surgical procedures to the structures which are dorsal of the spinal canal, the question arises as to whether the additional anterior procedure cannot be avoided, and the reconstructive measures of the anterior column can be carried out from dorsal, past the thecal sac and the nerve roots. The corresponding surgical procedures (posterior lumbar interbody fusion, PLIF, and transforaminal interbody fusion, TLIF), are established and clinical routine. Due to the tight anatomical space conditions, smaller cages are introduced from dorsal at the side of the thecal sac into the former intervertebral disc space. The direction of the access path thus dictates the permanent position of the implant. In most of these cage provisions, the fact that lumbar intervertebral discs are higher at the front than at the back, which results in a normal profile, “lordosis”, and the fact that an implant having as large an area as possible with a position near and parallel to the front edge ensures optimal load transfer, remain disregarded or poorly reconstructed.
The implants are inserted from a dorsal access into the space between the adjacent vertebrae after the removal of the intervertebral disc space and can then be rotated or pivoted into the coronal plane. Here, the convex region of the cage should be positioned in parallel to the front boundary of the intervertebral disc space.
In order to safely insert the implant into the intervertebral space, the implant should firstly be connected as rigidly as possible to the insertion tool. The implant is hingedly fastened to the distal end of an operating instrument for this purpose. By means of a screw mechanism, which is provided at the proximal end of the operating instrument, the implant can be pulled into coaxial alignment against the distal end of the tubular operating instrument and locked there in an angularly stable manner. Subsequently, the implant can be inserted, if necessary driven, into the intervertebral space under the protection of dura and emerging nerve root. Here, grooves form the path on the contact surfaces to the adjacent vertebrae and the specifically shaped implant tip (bullet nose). After passing the neural structures, the operating instrument, as far as possible, is pivoted in the transverse plane, the tension in the hinge is released by turning the handle, and the instrument is moved to the other side of the wound by pivoting.
In this modified position with respect to the operating instrument, the hinge connection to the implant is locked again by tensioning the locking lever, and the operating instrument is rotated back into the original position. This pivoting process is repeated until the implant in the former intervertebral disc space is rotated from the sagittal direction into the coronal plane.
This is described, for example, in DE 10 2013 005 692 A1 or EP 2 419 033 B1.
An arched interbody cage is known from WO 2005/041825 A1, which has a breakthrough at its two ends and a groove which leads into the breakthrough and serves for the engagement between a bar and a fastening cam, wherein the fastening cam can be moved in a groove in the cage. By actuating a screw mechanism, the cage can then additionally be firmly screwed to the operating instrument such that a rigid connection is established between the cage and the fastening device, and the cage can thus be driven into the intervertebral space. In order to release this rigid connection, the knurled screw is loosened again, the angle between the longitudinal axis of the cage and the longitudinal axis of the operating instrument is modified, and then the cage can be inserted further into the intervertebral space.
DE 10 2013 005 692 A1 discloses a tool with two different inserts for inserting spinal implants. The operating instrument, an insertion rod, comprises an outer tube which has a hollow handle on its proximal end for receiving a first inner rod. The inner rod is provided with a threaded region which extends beyond the distal end of the outer tube. The threaded region on the inner rod serves for fastening to the rear region of the implant which has a corresponding threaded bore there. The rear region of the implant can also be tensioned against the distal end region of the outer tube by means of the inner rod which can be moved with respect to the outer tube. For this purpose, the distal end region of the outer tube is at least partially adapted to the rear region of the implant. Locking is carried out by actuating a screw thread.
The previously described insertion tool is used to insert the cage into the intervertebral disc space until its rear end is at the level of the annulus of the intervertebral disc, said tool being unscrewed and exchanged for a special “ball” tool when the desired position is reached in order to drive the cage further in and at the same time to enable rotation/pivoting.
The need for several tools is cumbersome and increases the risk for the nerve structures that must be passed through during each change. In addition, control of the current implant position is temporarily lost in the depth of a (bleeding) wound, and, in some instances, the implants cannot be positioned in the exactly desired position with the tools known to date. In some implants, there is also the risk that they may become detached from the operating instrument during surgery. Once the implant has been inserted and detached from the operating instrument, it is also difficult to dock it back on the operating instrument for repositioning. Control over the movement of the implant is also difficult. In addition, the operating instrument interferes with an X-ray examination.
If it is necessary to change to another implant size, the guided and safe possibility for removal is not available.